1. Field of the Invention
The present invention relates to a dielectric ceramic composition used to obtain a monolithic type electronic component constructed by cofiring inner electrodes and ceramics, for example, a ceramic capacitor.
2. Description of the Prior Art
In a monolithic type electronic component such as a multilayer capacitor, a sintered body obtained by cofiring an electrode material constituting inner electrodes and dielectric ceramics is used. Meanwhile, when the multilayer capacitor is fabricated, a conventional dielectric material mainly composed of BaTiO.sub.3 is sintered at temperatures from 1300.degree. to 1500.degree. C. Accordingly, a noble metal such as Pd which is not melted at such sintering temperatures has been used as an electrode material constituting inner electrodes. However, the noble metal such as Pd is very high in cost. Consequently, when the number of inner electrodes is increased so as to achieve large capacity, the cost significantly rises, so that a cost reduction has been demanded.
Therefore, an attempt to use a low-cost base metal such as nickel as the electrode material constituting inner electrodes has been made. When inner electrodes constituted by the base metal such as nickel are used, however, the electrode material constituting the inner electrodes is liable to be oxidized. Accordingly, the dielectric material must be sintered in a reducing atmosphere. Consequently, if the dielectric material is sintered in such an atmosphere, an oxygen deficiency occurs, resulting in decreased insulation resistance.
In order to solve such a problem, a non-reduction type dielectric ceramic composition in which oxygen deficiency does not easily occur even if it is sintered in a reducing atmosphere by adding MgO and a rare earth oxide to BaTiO.sub.3 -CaZrO.sub.3 is proposed (Japanese Patent Laid-Open Gazette No. 157603/1987).
However, the dielectric ceramic composition disclosed in Japanese Patent Laid-Open Gazette No. 157603/1987 has a disadvantage in terms of sintering properties. More specifically, it is difficult to sinter the dielectric ceramic composition unless it is sintered at temperatures of not less than 1300.degree. C.